Air spring damper modules of this kind are primarily in use as spring struts on the forward axles in commercial vehicles. The needed space for mounting the spring and damping in a commercial vehicle is reduced by the coaxial telescopically engaged arrangement of air spring and shock absorber in an air spring damper module. This contributes to a wider spring track (Federspur) and a larger steering angle. The air spring flexible member with the closure plate and roll-off piston acts like an air spring known per se and the operating principle of the shock absorber likewise corresponds to the known state of the art. The shock absorbers are often closed in the built-in state at their upwardly directed ends with a closure plate. This closure plate is held tightly in position, for example, via an interlocking flanged connection of the outer tube of the shock absorber inwardly over the plate. The shock absorber rod is sealed off with a seal with respect to the closure plate. The flanged connection is a purely interlocking connection of the outer tube and the closure plate. The flanged connection is therefore especially sensitive to changing bending loads and plastic deformation.
In a typical embodiment of this type of air spring damper modules, the piston base has a support flange which is mounted on or in the opening of the piston base and is supported on the annular flange of the shock absorber in the mounted state. Furthermore, the roll-off piston mostly has additionally a buffer support which is pushed over the upper end of the shock absorber within the roll-off piston and is likewise supported on the annular flange of the shock absorber via the support flange of the piston base. The stop buffer or an additional spring, which is mounted in or on the closure plate of the air spring flexible member, impacts on an impact plate fixed to the upper end of the buffer support, for example, in the case of a bottoming out of the air spring. This construction functions to protect the roll-off piston at large loads against too great a deformation and to protect the interlocking flanged connection of the shock absorber against loads which are too great. It is disadvantageous that such roll-off pistons are complex, heavy and correspondingly cost intensive.
DE 197 55 549 C2 describes an air spring damper module wherein the roll-off piston lies flat on the upper end of the shock absorber. The total spring force and, in the case of a contact of the stop buffer with the piston cover, also the total buffer force supports itself therefore on the upper end of the shock absorber and the interlocking flanged connection of the outer tube arranged there. An annular flange on the outer tube is not present. In this solution, the closure of the outer tube of the shock absorber is subjected to very high loadings. If the closure is configured as an interlocking flanged connection, leaks and decreased damping power can occur because of the special sensitivity of the interlocking flanged connection with respect to mechanical damage or alternating bending loads.
U.S. Pat. No. 6,585,239 discloses a solution wherein the roll-off piston is spaced from the upper end of the shock absorber and is fixed in a manner not shown and the buffer force is taken up by a protective cover on the rolled end of the shock absorber. The protective cover must be tightly connected to the outer tube so that the protective cover does not separate during operation and to reliably prevent contact with the rolling of the outer tube. In the suggested solution, the assembly of the protective cover on the outer tube is possible only after the assembly of the roll-off piston on the shock absorber. A disassembly of the shock absorber, for example, for the purpose of exchange, is made very difficult or impossible because of the fixedly mounted protective cover.